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194 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3
of tidal water sweeps up the gradually narrowing channel of the Gulf and
causes an increasingly greater tidal range toward the Colorado river. At
Puerto Refugio the spring range is 11.8 feet, at Tepoca Bay 17.2 feet,
and at the mouth of the river 31.5 feet. These figures merely represent
the average differences between high and low water at the time of new or
full moon, and, since the author's visits to the Gulf were made during
times of maximum tidal difference in the winter and summer of 1940,
proportionally greater ranges were observed at all the stations visited.
Puerto Refugio, in particular, exhibited a most striking rise and fall of
the water level. A reef on the north side of the bay, exposed to a height of
at least 15 feet at lowest ebb, was completely submerged at high water.
At San Felipe on the Lower California coast quite near to the upper
extremity of the Gulf, large fishing boats were observed late in July of
1938 to be high and dry in a basin far above the reach of the high water
of that particular time. Yet, these boats are floated in on the crest of one
high-water tide and floated out again on another such crest.
Two thirds of the way up the Gulf lie a group of large islands and an
out jutting peninsula of land which together serve as a very decided hindrance to the movement of water up and down the Gulf. Above this narrow "bottleneck" is a large water area connected to the southern water
mass and the ocean at large only through these straits. Consequent upon
the tremendous movement of tidal water in and out of the northern area,
very strong currents develop in the channels between the islands. On
either side of San Esteban Island the currents are so powerful that anchorage is impossible and must be sought in protected bays of the south-
facing shore. The significance of these currents in regard to the general
distribution of algal populations will be taken up in a consideration of the
oxygen relations of these plants.
No discussion of general water movement in the Gulf is complete
without mention of the nature of wave action. Here again is a factor
playing an exceedingly important role in the oxygen relations of marine
algae. Unlike the outer coast, where powerful surf is the rule, the action
of waves in the Gulf of California is contrastingly slight. Except at times
of heavy winds and general storminess, the waters are essentially calm
and small waves prevail, breaking directly on the shore. Commonly there
is scarcely more than a strong lap of water on the beaches; and, wherever
protection is afforded, little more than a gentle surge. Toward the southern limits of the Gulf, however, increasingly heavy wave action is present,
reaching full proportions in the Cape district, where the collector, instead

194 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 3
of tidal water sweeps up the gradually narrowing channel of the Gulf and
causes an increasingly greater tidal range toward the Colorado river. At
Puerto Refugio the spring range is 11.8 feet, at Tepoca Bay 17.2 feet,
and at the mouth of the river 31.5 feet. These figures merely represent
the average differences between high and low water at the time of new or
full moon, and, since the author's visits to the Gulf were made during
times of maximum tidal difference in the winter and summer of 1940,
proportionally greater ranges were observed at all the stations visited.
Puerto Refugio, in particular, exhibited a most striking rise and fall of
the water level. A reef on the north side of the bay, exposed to a height of
at least 15 feet at lowest ebb, was completely submerged at high water.
At San Felipe on the Lower California coast quite near to the upper
extremity of the Gulf, large fishing boats were observed late in July of
1938 to be high and dry in a basin far above the reach of the high water
of that particular time. Yet, these boats are floated in on the crest of one
high-water tide and floated out again on another such crest.
Two thirds of the way up the Gulf lie a group of large islands and an
out jutting peninsula of land which together serve as a very decided hindrance to the movement of water up and down the Gulf. Above this narrow "bottleneck" is a large water area connected to the southern water
mass and the ocean at large only through these straits. Consequent upon
the tremendous movement of tidal water in and out of the northern area,
very strong currents develop in the channels between the islands. On
either side of San Esteban Island the currents are so powerful that anchorage is impossible and must be sought in protected bays of the south-
facing shore. The significance of these currents in regard to the general
distribution of algal populations will be taken up in a consideration of the
oxygen relations of these plants.
No discussion of general water movement in the Gulf is complete
without mention of the nature of wave action. Here again is a factor
playing an exceedingly important role in the oxygen relations of marine
algae. Unlike the outer coast, where powerful surf is the rule, the action
of waves in the Gulf of California is contrastingly slight. Except at times
of heavy winds and general storminess, the waters are essentially calm
and small waves prevail, breaking directly on the shore. Commonly there
is scarcely more than a strong lap of water on the beaches; and, wherever
protection is afforded, little more than a gentle surge. Toward the southern limits of the Gulf, however, increasingly heavy wave action is present,
reaching full proportions in the Cape district, where the collector, instead